Building automation products in industrial and commercial buildings perform a variety of tasks from regulating temperature to closing down ventilation systems during fires. Building automation products typically accomplish this by controlling power supplied to various equipment, such as motors and heating elements. Controlling a power supply can be accomplished through power modulation, but more commonly controlling a power supply is accomplished though a binary on-off operation.
Further, building automation products in industrial and commercial buildings are typically comprised of a control system and a distribution of numerous diverse apparatus, such as sensors and relays. These apparatus are typically comprised of housing assemblies which house printed circuit board assemblies. Such a printed circuit board assembly typically includes a printed circuit board populated with diverse components. Such a printed circuit board assembly may comprise either a single electrical circuit or multiple electrical circuits.
Printed circuit boards come in a variety of types. The types of printed circuit boards are similar to each other in the senses of being made from a substrate of suitable dielectric strength for an intended application voltage and of incorporating conductive pathways known as traces used to make circuits. Within those circuits, the traces electrically connect one location to another and may thereby be used to make connections to diverse components which are populated on the printed circuit board.
A small sampling of possible diverse components often populated on printed circuit boards include resistors, capacitors, inductors, electromechanical relays, diode bridges, light-emitting diodes (LEDs), etc.
A common example of a fully pre-wired printed circuit board assembly application related to building automation products is an emitter-follower voltage regulator circuit allowing for a range of control signal voltages (typically 10-30 volts either direct current (DC) or alternating current (AC), and up to AC line-to-neutral voltage through an additional resistor-capacitor circuit leg prior to a diode bridge) to energize an electromagnetic relay coil using rectified DC. When an electromagnetic relay coil is energized with sufficient electrical current, typically a switch (referred to as a pole) is activated inside the electromagnetic relay which makes an electrical contact, breaks an electrical contact, or both makes an electrical contact and breaks an electrical contact. An electrical contact affected by activation of the pole is referred to as a throw. Some electromagnetic relays comprise a plurality of throws. Further, some electromagnetic relays comprise a plurality of poles. Common electromagnetic relays used in the example application are either single-pole single-throw electromagnetic relays or single-pole double-throw electromagnetic relays, but other electromagnetic relays may be used. Usually for the example application, a light-emitting diode (LED) extends from the printed circuit board, and the LED illuminates when sufficient voltage is applied across the electromagnetic relay coil such that a sufficient electrical current will flow through the electromagnetic relay coil to activate the pole. Further, usually for the example application, there are at least two different sets of wires coupled to the printed circuit board. These sets of wires interface with circuits comprised in the printed circuit board assembly. In the example application, a first set of wires interface with the emitter-follower voltage regulator circuit, and a second set of wires interface with an electromagnetic relay electrical contact circuit. Additional circuits, wires, sets of wires, LEDs, and other components may be included in the printed circuit board assembly for additional utilities, such as for indicating load-side current.
Typical voltage ratings of the electromagnetic relay electrical contact circuit used in the example application noted above are either 277 volts AC or 480 volts AC.